Fe6.67(PO4)5.35(HPO4)0.65 and Fe6.23(PO4)4.45(HPO4)1.55: two new mixed‐valence iron phosphates

Two new mixed‐valence iron phosphates, namely heptairon pentaphosphate hydrogen phosphate, Fe_6.67(PO₄)_5.35(HPO₄)_0.65, and heptairon tetraphosphate bis(hydrogen phosphate), Fe_6.23(PO₄)_4.45(HPO₄)_1.55, have been synthesized hydrothermally at 973 K and 0.1 GPa. The structures are similar to that of Fe^II₃Fe^III₄(PO₄)₆ and are characterized by infinite chains of Fe polyhedra parallel to the [101] direction. These chains are formed by the Fe1O₆ and Fe2O₆ octahedra, alternating with the Fe4O₅ distorted pentagonal bipyramids, according to the stacking sequence ...Fe1–Fe1–Fe4–Fe2–Fe2.... The Fe3O₆ octahedra and PO₄ tetrahedra connect the chains together. Fe^II is localized on the Fe3 and Fe4 sites, whereas Fe^III is found in the Fe1 and Fe2 sites, according to bond‐valence calculations. Refined site occupancies indicate the presence of vacancies on the Fe4 site, explained by the substitution mechanism Fe^II + 2(PO₄³⁻) = vacancies + 2(HPO₄²⁻).     

Synthesis and crystal structure of mixed metal(III) tungstenyl(VI) ortho-pyrophosphates

The series of isotypic anhydrous ortho-pyrophosphates M^III(W^VIO₂)₂(P₂O₇)(PO₄) (M: Sc, V, Cr, Fe, Mo, Ru, Rh, In, Ir) was obtained via vapor phase moderated solid state reactions in sealed ampoules. The crystal structure of the phosphates M^III(W^VIO₂)₂(P₂O₇)(PO₄) (M: V, Ru, Rh) was solved from single crystal X-ray data (C2/c, Z = 16). Fairly regular MO₆ and distorted WO₆ octahedra share vertices with PO₄ and P₂O₇ units to form a 3D network. For the ortho-pyrophosphates with M: V³⁺, Cr³⁺, and Fe³⁺ the oxidation state of M is confirmed by magnetic measurements. ³¹P-MAS-NMR spectra of the diamagnetic phosphates M^III(W^VIO₂)₂(P₂O₇)(PO₄) (M: Sc, In, Ir) show surprisingly different isotropic chemical shifts for the seven phosphorus sites. V^III(W^VIO₂)₂(P₂O₇)(PO₄) occurs as equilibrium phase in the quasi-binary system (V_1–xW_x)OPO₄ at x = 0.67 and exhibits a small homogeneity range 0.60 ≤ x ≤ 0.67. The scandium compound shows a fully inverted occupancy of the M sites according to the formulation W(Sc_1/2W_1/2O₂)₂(P₂O₇)(PO₄).     

Synthesis and characterization of phosphates in molten systems Cs2O-P2O5-CaO-M2O3 (M—Al, Fe, Cr)

The crystallization of complex phosphates from the melts of Cs₂O-P₂O₅-CaO-M^III₂O₃ (M^III—Al, Fe, Cr) systems have been investigated at fixed value Cs/P molar ratios equal to 0.7, 1.0 and 1.3 and Са/Р=0.2 and Ca/М^III=1. The fields of crystallization of CsCaP₃O₉, β-Ca₂P₂O₇, Cs₂CaP₂O₇, Cs₃CaFe(P₂O₇)₂, Ca₉M^III(PO₄)₇ (M^III—Fe, Cr), Cs_0.63Ca_9.63Fe_0.37(PO₄)₇ and CsCa₁₀(PO₄)₇ were determined. Obtained phosphates were investigated using powder X-ray diffraction and FTIR spectroscopy. Novel whitlockite-related phases CsCa₁₀(PO₄)₇ and Cs_0.63Ca_9.63Fe_0.37(PO₄)₇ have been characterized by single crystal X-ray diffraction: space group R3c, a=10.5536(5) and 10.5221(4) Å, с=37.2283(19) and 37.2405(17) Å, respectively.     

La7O6(BO3)(PO4)2:Eu3+/Tb3+荧光材料的制备及其光致发光性能

采用优化的高温固相方法制备了稀土离子Eu³⁺和Tb³⁺掺杂的La₇O₆（BO₃）（PO₄）₂系荧光材料,并对其物相行为、晶体结构、光致发光性能和热稳定性进行了详细研究。结果表明,La₇O₆（BO₃）（PO₄）₂：Eu³⁺材料在紫外光激发下能够发射出红光,发射光谱中最强发射峰位于616 nm处,为⁵D₀→⁷F₂特征能级跃迁,Eu³⁺的最优掺杂浓度为0.08,对应的CIE坐标为（0.610 2,0.382 3）;La₇O₆（BO₃）（PO₄）₂：Tb³⁺材料在紫外光激发下能够发射出绿光,发射光谱中最强发射峰位于544 nm处,对应Tb³⁺的⁵D₄→⁷F₅能级跃迁,Tb³⁺离子的最优掺杂浓度为0.15,对应的CIE坐标为（0.317 7,0.535 2）。此外,对2种材料的变温光谱分析发现Eu³⁺和Tb³⁺掺杂的La₇O₆（BO₃）（PO₄）₂荧光材料均具有良好的热稳定性。     

A new disordered langbeinite‐type compound,K2Tb1.5Ta0.5P3O12, and Eu3+‐doped multicolour light‐emitting properties

For the first time, a new langbeinite‐type phosphate, namely potassium terbium tantalum tris(phosphate), K₂Tb_1.5Ta_0.5(PO₄)₃, has been prepared successfully using a high‐temperature flux method and has been structurally characterized by single‐crystal X‐ray diffraction. The results show that its structure can be described as a three‐dimensional open framework of [Tb_1.5Ta_0.5(PO₄)₃]_∞ interconnected by K⁺ ions. The Tb^III and Ta^V cations in the structure are disordered and occupy the same crystallographic sites. The IR spectrum, the UV–Vis spectrum, the morphology and the Eu³⁺‐activated photoluminescence spectroscopic properties were studied. A series of Eu³⁺‐doped phosphors, i.e. K₂Tb_1.5–xTa_0.5(PO₄)₃:xEu³⁺ (x = 0.01, 0.03, 0.05, 0.07, 0.10), were prepared via a solid‐state reaction and the photoluminescence properties were studied. The results show that under near‐UV excitation, the luminescence colour can be tuned from green through yellow to red by simply adjusting the Eu³⁺ concentration from 0 to 0.1, because of the efficient Tb³⁺→Eu³⁺ energy‐transfer mechanism.     

Synthesis,Structure, and Photoluminescence Properties of Novel KBaSc2(PO4)3:Ce3+/Eu2+/Tb3+ Phosphors for White‐Light‐Emitting Diodes

A series of novel KBaSc₂(PO₄)₃:Ce³⁺/Eu²⁺/Tb³⁺phosphors are prepared using a solid‐state reaction. X‐ray diffraction analysis and Rietveld structure refinement are used to check the phase purity and crystal structure of the prepared samples. Ce³⁺‐ and Eu²⁺‐doped phosphors both have broad excitation and emission bands, owing to the spin‐ and orbital‐allowed electron transition between the 4f and 5d energy levels. By co‐doping the KBaSc₂(PO₄)₃:Eu²⁺ and KBaSc₂(PO₄)₃:Ce³⁺ phosphors with Tb³⁺ ions, tunable colors from blue to green can be obtained. The critical distance between the Eu²⁺ and Tb³⁺ ions is calculated by a concentration quenching method and the energy‐transfer mechanism for Eu²⁺→Tb³⁺ is studied by utilizing the Inokuti–Hirayama model. In addition, the quantum efficiencies of the prepared samples are measured. The results indicate that KBaSc₂(PO₄)₃:Eu²⁺,Tb³⁺ and KBaSc₂(PO₄)₃:Ce³⁺,Tb³⁺ phosphors might have potential applications in UV‐excited white‐light‐emitting diodes.     

Neue Phosphate mit Eulytinstruktur,insbesondere Europium(II)-Verbindungen [1]

New Phosphates with Eulytine Structure, especially Europium(II) Compounds. A number of Eu(II) phosphates EuLn(PO₄)₃ have been prepared, where Ln? La, lanthanides, Y. All investigated compounds have colours from yellow to ockre and crystallize with the cubic structure of eulytine (Bi₄(SiO₄)₃). Eu(PO₄)₃ makes an exception, showing a lattice deformation to low symmetry. It converts to a cubic eulytine phase by partial oxydation. The peculiar run of the lattice constants of the Eu(II) compounds in the lanthanide series is compared with the behaviour of the analogous Sr, Pb, and Ba compounds. Moreover, the eulytine compounds Pb₃M^III(PO₄)₃ with M^III? V, Cr, Fe have been synthesized. Experiments with Ti^III yield solid solutions between Pb₃Ti^III(PO₄)₃ and Pb₇Ti^IV(PO₄)₆.     

Beiträge zum Koordinationsverhalten von Oxidionen in anorganischen Feststoffen. IV [1] Darstellung,Kristallstruktur und spektroskopische Charakterisierung von NiP4O11 und CaNiP2O7

Synthesis, Crystal Structures, and Spectroscopic Characterization of NiP₄O₁₁ and CaNiP₂O₇ From melts single crystals of NiP₄O₁₁ and CaNiP₂O₇ have been grown. These allowed refinement of the crystal structures (NiP₄O₁₁: C1¯, Z = 8, a = 12, 753(4)Å, b = 12.957(3)Å, c = 10.581(4)Å, α = 89.42(2)°, β = 116.96(2)°, γ = 90.20(2)°, R1 = 0.027, wR2 = 0.072 for 3058 I_o > 2σ (I_o), 3291 independent reflections, 290 parameters; CaNiP₂O₇: P1¯, Z = 2, a = 6.433(3)Å, b = 6.536(4)Å, c = 6.515(2)Å, α = 66.4(2)°, β = 87.5(2)°, γ = 82.7(2)°, R1 = 0.026, wR2 = 0.062 for 1624 I_o > 2σ (I_o), 2189 independent reflections, 101 parameter) and measurement of polarized electronic absorption spectra in the uv/vis/nir region (6000—32000 cm^—1). NiP₄O₁₁ is isotypic to the series of ultraphosphates MP₄O₁₁ (M = Mn, Fe, Co, Cu, Zn, Cd) that exhibit a two‐dimensional network formed from ten‐membered phosphate rings. CaNiP₂O₇ completes the series of diphosphates AMP₂O₇ (A: Ca, Sr, Ba; M = Cr — Zn) and is isotypic to CaCoP₂O₇. Ni²⁺ ions in both phosphates show distorted octahedral coordination. The electronic transitions associated with the chromophores [Ni²⁺O₆] are nicely reproduced by calculations within the framework of the angular overlap model (AOM). The parametrisation scheme leads to e_{σ, norm}(2.0Å) = 3690 cm^—1 and B = 896 cm^—1 (C/B = 4.2) for CaNiP₂O₇ and e_{σ, norm}(2.0Å) = 4150 cm^—1 and B = 948 cm^—1 (C/B = 4.5) for NiP₄O₁₁ (Δ_o(CaNiP₂O₇) = 6800 cm^—1; Δ_o(NiP₄O₁₁) = 7100 cm^—1).     

Study of the trivalent elements polyphosphates by thermal analysis

Mechanisms of formation of polyphosphates Me^III(PO₃)₃, where M ^III=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc, Fe, Ga, Al and Cr has been simulated by thermal analysis technique. Me^III oxides and ammonium dibasic phosphate (NH₄)₂HPO₄ were used as starting materials. For M ^III=La-Lu, Y and Fe three main stages were observed: 1. elimination of water and ammonia leading to the formation of ammonium tripolyphosphate (NH₄)₅P₃O₁₀; 2. reaction of the latter with Me₂^IIIO₃ and formation of acidic polyphosphates Me^IIIH₂P₃O₁₀ or their isomers Me^III(PO₃)₃·H₂O; 3. final loss of water and formation of Me^III(PO₃)₃. For Me ^III=Sc and Ga the second stage is prolonged and the polyphosphates form at higher temperatures. Aluminum and chromium polyphosphates are unstable. It is suggested that thermal behavior of the compounds is determined by Me^III ionic radii.     

Silver Vanadyl(IV) ortho‐Pyrophosphate: Synthesis,Crystal Structure,and Characterization of the (V≡O)2+ Group

Ag₆(V^IVO)₂(PO₄)₂(P₂O₇) was obtained by reaction of Ag₃PO₄ and (VO)₂P₂O₇ (sealed ampoule, 550 °C, 3 d). The crystal structure of the new mixed ortho‐pyrophosphate was determined from X‐ray single‐crystal data [Pnma, Z = 4, a = 12.759(3) Å, b = 17.340(4) Å, c = 6.418(1) Å, R₁ = 0.071, wR₂ = 0.184 for 3174 unique reflections with F_o > 4σ(F_o), 141 variables]. Ag⁺ ions are located in between layers [(V^IVO)₂(PO₄)₂(P₂O₇)]^6–. Equilibrium relations of the new phosphate to neighboring phases were determined. The electronic structure of the (V^IV≡O)²⁺ group was investigated by polarized electronic absorption spectroscopy (ν̃_1a = 9450 cm^–1, ν̃_1b = 9950 cm^–1, ν̃₂ = 14750 cm^–1), EPR spectroscopy [X‐ and Q‐band, powder and single crystal, orthorhombic crystal g‐tensor with g₁ = 1.9445(3), g₂ = 1.9521(3), g₃ = 1.9695(3)], and magnetic measurements (powder, μ_exp/μ_B = 1.71, Θ_p = –1.7 K).     

Kinetics and Mechanism of Oxidation of S2O32− by a Co‐Bound μ‐Amido‐μ‐Superoxo Complex

In acetate buffer media (pH 4.5–5.4) thiosulfate ion (S₂O₃^2?) reduces the bridged superoxo complex, [(NH₃)₄Co^III(μ‐NH₂,μ‐O₂)Co^III(NH₃)₄]⁴⁺ ( 1 ) to its corresponding μ‐peroxo product, [(NH₃)₄Co^III(μ‐NH₂,μ‐O₂)Co^III(NH₃)₄]³⁺ ( 2 ) and along a parallel reaction path, simultaneously S₂O₃^2? reacts with 1 to produce the substituted μ‐thiosulfato‐μ‐superoxo complex, [(NH₃)₄Co^III(μ‐S₂O₃,μ‐O₂)Co^III(NH₃)₄]³⁺ ( 3 ). The formation of μ‐thiosulfato‐μ‐superoxo complex ( 3 ) appears as a precipitate which on being subjected to FTIR shows absorption peaks that support the presence of Co(III)‐bound S‐coordinated S₂O₃^2? group. In reaction media, 3 readily dissolves to further react with S₂O₃^2? to produce μ‐thiosulfato‐μ‐peroxo product, [(NH₃)₄Co^III(μ‐S₂O₃,μ‐O₂)Co^III(NH₃)₄]²⁺ ( 4 ). The observed rate (k₀) increases with an increase in [T_Thio] ([T_Thio] is the analytical concentration of S₂O₃^2?) and temperature (T), but it decreases with an increase in [H⁺] and the ionic strength (I). Analysis of the log A_t versus time data (A is the absorbance of 1 at time t) reveals that overall the reaction follows a biphasic consecutive reaction path with rate constants k₁ and k₂ and the change of absorbance is equal to {a₁ exp(–k₁t) + a₂ exp(–k₂t)}, where k₁ > k₂.     

K3Eu5(PO4)6: hydrothermal synthesis,crystal structure and photoluminescence properties

An anhydrous orthophosphate, K₃Eu₅(PO₄)₆ (tripotassium pentaeuropium hexaphosphate), has been prepared by a high‐temperature solid‐state reaction combined with hydrothermal synthesis, and its crystal structure was determined by single‐crystal X‐ray diffraction analysis (SC‐XRD). The results show that the compound crystallizes in the monoclinic space group C2/c and the structure features a three‐dimensional framework of [Eu₅(PO₄)₆]_∞, with the tunnel filled by K⁺ ions. The IR spectrum, UV–Vis spectrum and luminescence properties of polycrystalline samples of K₃Eu₅(PO₄)₆, annealed at temperatures of 650, 700, 750, 800 and 850 °C, were investigated. Although with a full Eu³⁺ concentration (9.96 × 10²¹ ions cm^?3), the self‐activated phosphor K₃Eu₅(PO₄)₆ shows s strong luminescence emission intensity with a quantum yield of 37%. Under near‐UV light excitation (393 nm), the series of samples shows the characteristic emissions of Eu³⁺ ions in the visible region from 575 to 715 nm. The sample sintered at 800 °C gives the strongest emission and its lifetime sintered at 800 °C (1.88 ms) is also the longest of all.     

Crystal structures of lazulite-type oxidephosphates TiTi3O3(PO4)3 and M4Ti27O24(PO4)24 (M=Ti, Cr, Fe)

Single crystals of the oxidephosphates Ti^IIITi^IV₃O₃(PO₄)₃ (black), Cr^III₄Ti^IV₂₇O₂₄(PO₄)₂₄ (red-brown, transparent), and Fe^III₄Ti^IV₂₇O₂₄(PO₄)₂₄ (brown) with edge-lengths up to 0.3 mm were grown by chemical vapour transport. The crystal structures of these orthorhombic members (space group F2dd ) of the lazulite/lipscombite structure family were refined from single-crystal data [Ti^IIITi^IV₃O₃(PO₄)₃: Z=24, a=7.3261(9) Å, b=22.166(5) Å, c=39.239(8) Å, R₁=0.029, wR₂=0.084, 6055 independent reflections, 301 variables; Cr^III₄Ti^IV₂₇O₂₄(PO₄)₂₄: Z=1, a=7.419(3) Å, b=21.640(5) Å, c=13.057(4) Å, R₁=0.037, wR₂=0.097, 1524 independent reflections, 111 variables; Fe^III₄Ti^IV₂₇O₂₄(PO₄)₂₄: Z=1, a=7.4001(9) Å, b=21.7503(2) Å, c=12.775(3) Å, R₁=0.049, wR₂=0.140, 1240 independent reflections, 112 variables). For Ti^IIITi^IVO₃(PO₄)₃ a well-ordered structure built from dimers [Ti^III,IV₂O₉] and [Ti^IV,IV₂O₉] and phosphate tetrahedra is found. The metal sites in the crystal structures of Cr₄Ti₂₇O₂₄(PO₄)₂₄ and Fe₄Ti₂₇O₂₄(PO₄)₂₄, consisting of dimers [M^IIITi^IVO₉] and [Ti^IV,IV₂O₉], monomeric [Ti^IVO₆] octahedra, and phosphate tetrahedra, are heavily disordered. Site disorder, leading to partial occupancy of all octahedral voids of the parent lipscombite/lazulite structure, as well as splitting of the metal positions is observed. According to Guinier photographs Ti^III₄Ti^IV₂₇O₂₄(PO₄)₂₄ (a=7.418(2) Å, b=21.933(6) Å, c=12.948(7) Å) is isotypic to the oxidephosphates M^III₄Ti^IV₂₇O₂₄(PO₄)₂₄ (M^III: Cr, Fe). The UV/vis spectrum of Cr₄Ti₂₇O₂₄(PO₄)₂₄ reveals a rather small ligand-field splitting Δ_o=14,370 cm⁻¹ and a very low nephelauxetic ratio β=0.72 for the chromophores [Cr^IIIO₆] within the dimers [Cr^IIITi^IVO₉].     

Synthesis and structural determination of the first eight-coordinate rare earth metal complex with a six-member ring, (NH4)[EuIII(pdta)(H2O)] · H2O

(NH₄)[Eu^III(pdta)(H₂O)]?·?H₂O has been synthesized and characterized by infrared spectrum, fluorescence spectrum, elemental analyses and single-crystal X-ray diffraction techniques. It crystallizes in the monoclinic system with space group P2₁/n, a?=?12.7700(15)?Å, b?=?9.3885(11)?Å, c?=?14.4070(18)?Å, α?=?90°, β?=?95.950(2)°, γ?=?90°, V?=?1718.0(4)?ų, Z?=?4, M?=?508.28, D _c?=?1.965?g?cm^?3, μ?=?3.708?mm^?1, F(000)?=?1108. The structure was refined to R ₁?=?0.0238 for 3469 observed reflections (I?>?2σ(I)). The Eu^IIIN₂O₆ part in the [Eu^III(pdta)(H₂O)]^? complex anion has an eight-coordinate structure with a distorted square anti-prismatic conformation, in which six coordination positions, two nitrogen atoms and four oxygen atoms are from one pdta (=propylenediaminetetraacetic acid) ligand, the seventh position is an oxygen (O(8A)) from another pdta and the eighth coordination site is occupied by a water molecule. (NH₄)[Eu^III(pdta)(H₂O)]?·?H₂O is the first eight-coordinate complex with a six-member ring in the rare earth metal complexes with aminopolycarboxylic acid ligands.     

Refinement of the Superstructure of C-Type Gallium Tris(metaphosphate), Ga(PO3)3

Single crystals of Ga(PO₃)₃ were grown in polyphosphoric acid melts by heating a mixture of Ga₂O₃ and H₃PO₄ (350 °C, 7 d). The compound belongs to the series of metaphosphates M^III(PO₃)₃ forming the C-type structure (monclinic, Cc, Z = 12, a = 13.0058(21), b = 18.915(3), c = 9.3105(15) Å, β = 126.900(11), 5348 independent reflections (I > 0); 354 variables; 39 atoms in asymetric unit; R1 = 0.048, wR2 = 0.1034). The structure is characterized by a superstructure with tripled monoclinic b-axis. Three crystallographically independent Ga^IIIO₆ octahedra (d¯(Ga–O) = 1.950 Å) are linked by ¹_∞(PO₃)^– chains.     

La_7O_6(BO_3)(PO_4)_2∶Eu~(3+)/Tb~(3+)荧光材料的制备及其光致发光性能

采用优化的高温固相方法制备了稀土离子Eu~(3+)和Tb~(3+)掺杂的La_7O_6(BO_3)(PO_4)_2系荧光材料,并对其物相行为、晶体结构、光致发光性能和热稳定性进行了详细研究。结果表明,La_7O_6(BO_3)(PO_4)_2∶Eu~(3+)材料在紫外光激发下能够发射出红光,发射光谱中最强发射峰位于616 nm处,为5D0→7F2特征能级跃迁,Eu~(3+)的最优掺杂浓度为0.08,对应的CIE坐标为(0.610 2,0.382 3);La_7O_6(BO_3)(PO_4)_2∶Tb~(3+)材料在紫外光激发下能够发射出绿光,发射光谱中最强发射峰位于544 nm处,对应Tb~(3+)的5D4→7F5能级跃迁,Tb~(3+)离子的最优掺杂浓度为0.15,对应的CIE坐标为(0.317 7,0.535 2)。此外,对2种材料的变温光谱分析发现Eu~(3+)和Tb~(3+)掺杂的La_7O_6(BO_3)(PO_4)_2荧光材料均具有良好的热稳定性。     

K3[Fe3.26V0.74(OH)O(PO4)4(H2O)2]·2H2O: a synthetic leucophosphite

A new iron(III)/vanadium(III) phosphate, K₃[Fe_3.26V_0.74(OH)O(PO₄)₄(H₂O)₂]·2H₂O (1), has been obtained by hydrothermal synthesis and characterized by single crystal X-ray diffraction, Scanning electron microscopy–energy dispersive X-ray spectroscopy, Inductively coupled plasma atomic emission spectroscopy (ICP), thermogravimetric analysis, and FTIR spectroscopy. Single crystal X-ray diffraction reveals a 3D open framework (monoclinic, space group P2₁/n, a?=?9.6391(7)?Å, b?=?9.8063(7)?Å, c?=?9.7268(7)?Å, β?=?100.71(1)°, and V?=?903.38(11)?ų). This structure presents Fe^III and V^III in a 4.4?:?1?M ratio with the metal ions in two different crystallographic sites. Both metallic centers have distorted octahedral environments, linked by PO₄ tetrahedra, forming channels along the a-axis. The asymmetric unit of K₃[Fe_3.26V_0.74(OH)O(PO₄)₄(H₂O)₂]·2H₂O presents a {M₄(OH)O(PO₄)₄(H₂O)₂}^3? anionic entity, charge balanced by three K⁺, which are located within the channels. It is also possible to distinguish M₄O₂ units whose M^III polyhedra are linked by vertex and edges.     

Eu2+ & Mn2+‐Coactivated Ba3Gd(PO4)3 Orange‐Yellow‐Emitting Phosphor with Tunable Color Tone for UV‐Excited White LEDs

A novel orange‐yellow‐emitting Ba₃Gd(PO₄)₃:x Eu²⁺,y Mn²⁺ phosphor is prepared by high‐temperature solid‐state reaction. The crystal structure of Ba₃Gd(PO₄)₃:0.005 Eu²⁺,0.04 Mn²⁺ is determined by Rietveld refinement analysis on powder X‐ray diffraction data, which shows that the cations are disordered on a single crystallographic site and the oxygen atoms are distributed over two partially occupied sites. The photoluminescence excitation spectra show that the developed phosphor has an efficient broad absorption band ranging from 230 to 420 nm, perfectly matching the characteristic emission of UV‐light emitting diode (LED) chips. The emission spectra show that the obtained phosphors possess tunable color emissions from yellowish‐green through yellow and ultimately to reddish‐orange by simply adjusting the Mn²⁺ content (y) in Ba₃Gd(PO₄)₃:0.005 Eu²⁺,y Mn²⁺ host. The tunable color emissions origin from the change in intensity between the 4f–5d transitions in the Eu²⁺ ions and the ⁴T₁‐⁶A₁ transitions of the Mn²⁺ ions through the energy transfer from the Eu²⁺ to the Mn²⁺ ions. In addition, the mechanism of the energy transfer between the Eu²⁺ and Mn²⁺ ions are also studied in terms of the Inokuti–Hirayama theoretical model. The present results indicate that this novel orange‐yellow‐emitting phosphor can be used as a potential candidate for the application in white LEDs.     

Synthese und Kristallstruktur von Te3O3(PO4)2, einer Verbindung mit fünffach koordiniertem Tellur(IV)

Synthesis and Crystal Structure of Te₃O₃(PO₄)₂, a Compound with 5‐fold Coordinate Tellurium(IV) Polycrystalline Te₃O₃(PO₄)₂ is formed during controlled dehydration of (Te₂O₃)(HPO₄) with (Te₈O₁₀)(PO₄)₄ as an intermediate product. Colourless single crystals were prepared by heating stoichiometric amounts of the binary oxides P₂O₅ und TeO₂ in closed silica glass ampoules at 590 °C for 8 hours. The crystal structure (P2₁/c, Z = 4, α = 12.375(2), b = 7.317(1), c = 9.834(1)Å, β = 98.04(1)°, 1939 structure factors, 146 parameters, R[F² > 2σ(F²)] = 0.0187, wR2(F² all) = 0.0367) was determined from four‐circle diffractometer data and consists of [TeO₅] polyhedra und PO₄ tetrahedra as the main building units. The framework structure is made up of cationic zigzag‐chains of composition [Te₂O₃]²⁺ which extend parallel to [001] and anionic [Te(PO₄)₂]^2— units linked laterally to these chains. This leads to the formation of [Te₂O₃][Te(PO₄)₂] layers parallel to the bc plane which are interconnected via weak Te‐O bonds.     

Homo‐ and Heterovalent Polynuclear Cerium and Cerium/Manganese Aggregates

Reactions of Ce^III(NO₃)₃?6 H₂O or (NH₄)₂[Ce^IV(NO₃)₆] with Mn‐containing starting materials result in seven novel polynuclear Ce or Ce/Mn complexes with pivalato (^tBuCO ) and, in most cases, auxiliary N,O‐ or N,O,O‐donor ligands. With nuclearities ranging from 6–14, the compounds present aesthetically pleasing structures. Complexes [Ce^IV₆(μ₃‐O)₄(μ₃‐OH)₄(μ‐O₂C^tBu)₁₂] ( 1 ), [Ce^IV₆Mn^III₄(μ₄‐O)₄(μ₃‐O)₄(O₂C^tBu)₁₂(ea)₄(OAc)₄]?4 H₂O?4 MeCN (ea^?=2‐aminoethanolato; 2 ), [Ce^IV₆Mn^III₈(μ₄‐O)₄(μ₃‐O)₈(pye)₄(O₂C^tBu)₁₈]₂[Ce^IV₆(μ₃‐O)₄(μ₃‐OH)₄(O₂C^tBu)₁₀(NO₃)₄] [Ce^III(NO₃)₅(H₂O)]?21 MeCN (pye^?=pyridine‐2‐ethanolato; 3 ), and [Ce^IV₆Ce^III₂Mn^III₂(μ₄‐O)₄(μ₃‐O)₄(^tbdea)₂(O₂C^tBu)₁₂(NO₃)₂(OAc)₂]?4 CH₂Cl₂ (^tbdea^2?=2,2′‐(tert‐butylimino]bis[ethanolato]; 4 ) all contain structures based on an octahedral {Ce^IV₆(μ₃‐O)₈} core, in which many of the O‐atoms are either protonated to give (μ₃‐OH)^? hydroxo ligands or coordinate to further metal centers (Mn^III or Ce^III) to give interstitial (μ₄‐O)^2? oxo bridges. The decanuclear complex [Ce^IV₈Ce^IIIMn^III(μ₄‐O)₃(μ₃‐O)₃(μ₃‐OH)₂(μ‐OH)(bdea)₄(O₂C^tBu)_9.5(NO₃)_3.5(OAc)₂]?1.5 MeCN (bdea^2?=2,2′‐(butylimino]bis[ethanolato]; 5 ) contains a rather compact Ce^IV₇ core with the Ce^III and Mn^III centers well‐separated from each other on the periphery. The aggregate in [Ce^IV₄Mn^IV₂(μ₃‐O)₄(bdea)₂(O₂C^tBu)₁₀(NO₃)₂]?4 MeCN ( 6 ) is based on a quasi‐planar {Mn^IV₂Ce^IV₄(μ₃‐O)₄} core made up of four edge‐sharing {Mn^IVCe^IV₂(μ₃‐O)} or {Ce^IV₃(μ₃‐O)} triangles. The structure of [Ce^IV₃Mn^IV₄Mn^III(μ₄‐O)₂(μ₃‐O)₇(O₂C^tBu)₁₂(NO₃)(furan)]?6 H₂O ( 7 ?6 H₂O) can be considered as {Mn^IV₂Ce^IV₂O₄} and distorted {Mn^IV₂Mn^IIICe^IVO₄} cubane units linked through a central (μ₄‐O) bridge. The Ce₆Mn₈ equals the highest nuclearity yet reported for a heterometallic Ce/Mn aggregate. In contrast to most of the previously reported heterometallic Ce/Mn systems, which contain only Ce^IV and either Mn^IV or Mn^III, some of the aggregates presented here show mixed valency, either Mn^IV/Mn^III (see 7 ) or Ce^IV/Ce^III (see 4 and 5 ). Interestingly, some of the compounds, including the heterovalent Ce^IV/Ce^III 4 , could be obtained from either Ce^III(NO₃)₃?6 H₂O or (NH₄)₂[Ce^IV(NO₃)₆] as starting material.